Steam Assisted Gravity Drainage (SAGD) is a technique for recovering heavy crude oil and/or bitumen from geologic formations, and generally includes heating the bitumen through an injection borehole until it has a viscosity low enough to allow it to flow into a recovery borehole. As used herein, “bitumen” refers to any combination of petroleum and matter in the formation and/or any mixture or form of petroleum, specifically petroleum naturally occurring in a formation that is sufficiently viscous as to require some form of heating or diluting to permit removal from the formation.
SAGD techniques exhibit various problems that inhibit productivity and efficiency. For example, portions of a heat injector may overheat and warp causing difficulty in extracting an introducer string through the injection borehole. Also, difficulties in maintaining or controlling temperature of the liquid bitumen may pose difficulties in extracting the bitumen. Other problems include the requirement for large amounts of energy to deliver sufficient heat to the formation.